Showing papers on "Homolysis published in 1975"
TL;DR: In this article, the relative rates of cyclization of a number of related radicals have been determined, consistent with the hypothesis that the transition state for homolytic addition to an olefin bond is formed by primary interaction of the semi-occupied orbital with one lobe of the π* orbital.
Abstract: Aryl radicals generated by interaction of tributylstannane with aryl iodides containing unsaturated ortho-substituents cyclize regiospecifically to afford products containing the newly formed-radical centre exocyclic to the newly-formed ring. The relative rates of cyclization of a number of related radicals have been determined. The results are consistent with the hypothesis that the transition state for homolytic addition to an olefin bond is formed by primary interaction of the semi-occupied orbital with one lobe of the π* orbital.
42 citations
TL;DR: In this paper, the ERS spectra of a number of radicals generated by homolytic addition at one of the double bonds in the diolefins rapidly undergo cyclization to afford product radicals containing five-membered rings.
Abstract: ESR spectra have been recorded for a number of radicals generated in a flow cell by interaction of diallylmalonic acid, diallyl ether, diallylamine, and related compounds with amino, hydroxyl, and phenyl radicals in aqueous solution. The results indicate that the radicals initially formed by homolytic addition at one of the double bonds in the diolefins rapidly undergo cyclization to afford product radicals containing five-membered rings.
22 citations
19 citations
TL;DR: In this article, the authors showed that in the presence of a nitroso compound R′NO (R′=But or 2,3,5,6-Me4C6H) under anaerobic conditions in H2O, Me2SO, or PhOH-CHCl3, affords the spin-trapped nitroxide R′N(Ȯ)R.
Abstract: Irradiation of vitamin B12 coenzyme or ethylcobalamin (LCoIII–R) in the presence of a nitroso compound R′NO (R′= But or 2,3,5,6-Me4C6H) under anaerobic conditions in H2O (R′= But), Me2SO, or PhOH–CHCl3, affords the spin-trapped nitroxide R′N(Ȯ)R.
18 citations
15 citations
TL;DR: The pyrolysis of styryl sulphoxides yields benzothiophens in 40-50% yield as discussed by the authors, indicating that intra-molecular cyclization of the S −OH bond of an intermediate sulphenic acid is a favorable process.
Abstract: The pyrolysis of styryl sulphoxides yields benzothiophens in 40–50% yield, indicating that intra-molecular cyclization of the styrylthiyl radical, which may be formed by homolysis of the S–OH bond of an inter-mediate sulphenic acid, is a favourable process; pyrolysis of styryl sulphides, and bis-(β-methyl styryl) disulphide also gave benzothiophens under similar conditions.
14 citations
TL;DR: In this paper, it was shown that triphenylphosphine substitution in decalin or cyclohexane can be achieved via initial reversible homolytic fission of the Mn-Mn bond followed by an associative interchange reaction of triphensyl phosphite with the Mn(CO)4PPh3 radical.
Abstract: Evidence is presented that the substitution by triphenyl phosphite, in decalin or cyclohexane of one triphenylphosphine in the complex [Mn(CO)4PPh3]2 occurs via initial reversible homolytic fission of the Mn–Mn bond followed by an associative interchange reaction of triphenyl phosphite with the Mn(CO)4PPh3 radical.
13 citations
13 citations
TL;DR: Pair substitution CIDNP effects have been utilized to study SH2 reactions of benzoyloxyl radicals at the metal centres of group IV (Pb and Sn) and transition-metal alkyls as discussed by the authors.
Abstract: Pair substitution CIDNP effects have been utilized to study SH2 reactions of benzoyloxyl radicals at the metal centres of group IV (Pb and Sn) and transition-metal alkyls.
11 citations
TL;DR: In this article, a comparative study of the oxidation of oct-1-ene by lead(IV), thallium(III), and mercury(II) acetates in methanol has been extended to other solvents and to the internal olefin, trans-oct-4-ene.
Abstract: The comparative study of the oxidation of oct-1-ene by lead(IV), thallium(III), and mercury(II) acetates in methanol has been extended to other solvents and to the oxidation of an internal olefin, trans-oct-4-ene. The general rules developed for the methanol system are found to be applicable to these solvents. In acetic acid, incorporation of an acetoxy-substituent on C-2 of oct-1-ene followed by decomposition of the organometallic adduct via an acetoxonium ion gives a high yield of hydroxy-acetates. This yield is boosted in lead(IV) oxidations by the addition of water to the system. The adduct from mercury(II) oxidation is stable but reduction of it with borohydride does not appear to offer a clean means of adding a carboxylic acid across a double bond: substantial reduction of the ester function occurs. There appear to be severe steric constraints to the oxidation of trans-oct-4-ene by initial electrophilic addition of the metal acetates but when this does occur there is a stereoselective preference for anti-addition. However, the major products are allylic. It is suggested that, in the case of lead(IV) oxidations, these arise by a homolytic process; indeed there is no evidence of heterolytic attack of this oxidant on oct-4-ene.
10 citations
TL;DR: In this paper, a series of alkyl-substituted 9-chloroacridines and 9-acridones have been synthesised from N-arylanthranilic acids; the n.m. and u.v. spectra of the chloro acridines were investigated; and Petrow's mechanism for conversion of 2-anilinomethylenecyclohexanones into tetrahydroacridine was confirmed.
Abstract: A series of alkyl-substituted 9-chloroacridines and 9-acridones have been synthesised from N-arylanthranilic acids; the n.m.r. spectra of the chloroacridines and the i.r. and u.v. spectra of the 9-acridones have been investigated. 2-Cyclohexyloxybenzoic acid was formed from 2-chlorobenzoic acid and the cyclohexanol used as solvent in some Ullmann reactions. Petrow's mechanism for the conversion of 2-anilinomethylenecyclohexanones into tetrahydroacridines has been confirmed. A steric effect is displayed in the homolytic α-bromination of 2- and 4-alkyl-9-chloroacridines.
TL;DR: In this paper, it was shown that pyrolysis of the secondary amine depends on its homolytic fission to benzyl and phenylamine free radicals.
Abstract: Heating N-benzylaniline resulted in migration of the benzyl group to the ortho- and para-positions of the aniline nucleus. Ammonia, toluene, biphenyl, diphenylmethane, dibenzyl, trans-stilbene, aniline, together with 9-phenylacridine, and 2,3-diphenylindole, were also formed.When phenol, quinoline, or isoquinoline were used as solvents, the normal rearrangement products were accompanied by 2- and 4-benzylphenols, 3-benzylquinoline, 2- and 4-(aminophenyl)quinoline, 4-benzylisoquinoline, and 1-(aminophenyl)isoquinolines.It is concluded that the pyrolysis of the secondary amine depends on its homolytic fission to benzyl and phenylamine free radicals. Homolysis of some initially separated products was also observed.
TL;DR: In this article, diphenylphosphinothioic chlorides were allowed to react in tetrahydrofuran (THF) in the presence of metal or metal salts at 120-150°C.
Abstract: Diphenylphosphinic (1) and diphenylphosphinothioic chlorides (2) were allowed to react in tetrahydrofuran (THF) in the presence of metal or metal salts at 120–150°C. In the cases of lithium and magnesium, [Ph2PX]–(X=O, S) thus formed attacked the α-carbon of THF to give ring-opening products, which were produced by deoxygenation, sulfurization, and reaction with 1 and 2. In the cases of iron, copper, and their salts, O-4-chlorobutyl diphenylphosphinate (12) and diphenylphosphinothioate (13) were obtained in a homolytic fashion. The formation mechanisms have been discussed.
TL;DR: In this paper, a Wurtz-type coupling reaction was used to synthesize 2-trimethylstannyl-l,3-butadiene, which was submitted to direct excitation by light of 253.7 or 228.8 nm in cyclohexane solution.
TL;DR: The main products of the 185 nm photolysis of liquid methyl n-propyl ether (quantum yields in parentheses) are n-propanol (0.70), methane (0.,29), sec-butyl methyl ether (0,20), methanol ( 0.16), propionaldehyde (0).
Abstract: The main products of the 185 nm photolysis of liquid methyl n-propyl ether (quantum yields in parentheses) are n-propanol (0.70), methane (0.29), sec-butyl methyl ether (0.20), methanol (0.16), propionaldehyde (0.13), 3,4-dimethoxyhexane (0.09), ethane (0.08), and ethyl n-propyl ether (0.08). The quantum yields of further 24 minor products have been measured. The quantum yield of the sum of primary photochemical processes, the main ones of which are the homolytic scissions of the C–O bonds (reactions i and ii), is close to unity.Reaction (i) is favoured over reaction (ii) by nearly a factor of five. The elimination of molecular methane (iii) is the only other process of importance. C–H and C–C bond splitting is marginal.
TL;DR: In this article, the homolytic process of the reaction of 1 with phenyllithium in toluene has been investigated and the results indicate that these reactions proceed through a homolysis process.
Abstract: 3,4-Dihydro-2,4,6-triphenyl-2H-1,2,4,5-tetrazin-1-yl (1) reacted with ethyl- and butyllithiums to give 1-ethyl- and 1-butyl-2,4,6-triphenyl-1,2,3,4-tetrahydro-1,2,4,5-tetrazines respectively On the other hand, biphenyl and 1-benzyl-2,4,6-triphenyl-1,2,3,4-tetrahydro-1,2,4,5-tetrazine were given by the reaction of 1 with phenyllithium in toluene Thus, the results indicate that these reactions proceed through a homolytic process
TL;DR: In this paper, the effect of benzophenone O-acyloximes (I) in benzene or toluene effects aromatic substitution on the solvents by diphenylmethaniminyl radicals (IV) to give Ndiphenylmethyleneaniline (II) or N-d...
Abstract: Irradiation of benzophenone O-acyloximes (I) in benzene or toluene effects aromatic substitution on the solvents by diphenylmethaniminyl radicals (IV) to give N-diphenylmethyleneaniline (II) or N-d...
TL;DR: In this article, free radicals obtained from 3- and 8-aminoquinolines were studied in various aromatic substrates and isomer percent, reaction yields, and overall reactivities towards benzene were recorded.
TL;DR: In this paper, it was shown that the yield of substituted benzene product depends upon the p -substituent of the polyfluoroaniline and was greatest for tetrafluoro-p -anisidine.
TL;DR: In this article, a bimolecular homolytic substitution process was used for 3,4-dihydro-2,4,6-triphenyl-1,2, 4,5-tetrazin-1(2H)-yl with Grignard reagents.
Abstract: Reactions of 3,4-dihydro-2,4,6-triphenyl-1,2,4,5-tetrazin-1(2H)-yl with Grignard reagents have been investigated, and these reactions have been found to proceed through a bimolecular homolytic substitution process.
TL;DR: The main products of the photolysis (λ 185 nm) of liquid methoxyethanol (quantum yields in parentheses) are H2(0.27), CH2O (0.19), CH4(0.,15), methoxyacetaldehyde (0.,10), ethanol (0,09), and methanol (0).
Abstract: The main products of the photolysis (λ 185 nm) of neat liquid methoxyethanol (quantum yields in parentheses) are H2(0.27), CH2O (0.19), CH4(0.15), methoxyacetaldehyde (0.10), ethylene glycol (0.10), ethanol (0.09), and methanol (0.05). The quantum yields of 34 products altogether have been measured. It is concluded that there are two major reactions (i) and (ii), involving homolytic splitting of the O–H and O–CH3 bonds. Molecular HOCH2CH2OCH3→ H·+·OCH2CH2OCH3(i), → HOCH2CH2O·+·CH3(ii) fragmentation reactions and the homolytic scission of other bonds play a minor role. In the presence of N2O (saturated solution)ϕ(H2) is decreased by ca. 10% while ϕ(N2) is 0.08 indicating that photoionisation processes are only moderately important. In dilute aqueous solution ϕ(H2) and ϕ(CH4) are strongly decreased.
TL;DR: In this paper, a homolytic hydroxyalkylation of quinoline derivatives by redox systems is described, where the nucleophilic character at the heteroaromatic ring of the radicals is exploited.
Abstract: Homolytic hydroxyalkylation of quinoline derivatives by redox systems is described. The direct introduction of hydroxyalkyl groups into heteroaromatic ring of quinoline derivatives has been achieved by means of hydrogen peroxide. The good yields and the complete selectivity obtained are due to the nucleophilic character at heteroaromatic ring of the hydroxyalkyl radicals. It is useful to apply this reaction to other synthetic reactions.